Generally, in a wireless communications system, the communications system's capacity may be significantly improved when a transmitter (such as a base station (BS), NodeB, enhanced NodeB (eNB), and so on, in a downlink (DL) channel) has full or partial knowledge of a channel over which it will be transmitting. Information related to the channel may be referred to as channel information. Channel information may be obtained by the transmitter over a reverse feedback channel. A receiver (such as a mobile station (MS), User Equipment (UE), mobile, user, and so forth, in a DL channel) of transmissions made by the transmitter may transmit channel information back to the transmitter over the reverse feedback channel. The receiver may estimate the channel, generate the channel information, and feed the channel information back to the transmitter.
In Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release-9 and earlier compliant communications systems, a reverse feedback channel referred to as a physical uplink control channel (PUCCH) is used to allow receivers to transmit (feedback) channel information to the transmitter. As an example, up to 13 information bits (information prior to encoding) may be transmitted in a single PUCCH packet. Actual PUCCH packet payload is 20 coded bits.
In 3GPP LTE Release-9 and earlier compliant communications systems, there may be several types of channel information, including:
1. Rank Indicator (RI)—an indication of a number of spatial layers that can be supported by a communications channel. The RI may be fedback infrequently.
2. Wideband Precoding Matrix Indicator (PMI) and/or Channel Quality Indicator (CQI)—indications of channel quality or a codebook quantized version of the channel quality for a wideband channel. The wideband PMI/CQI may be fedback frequently.
3. Subband CQI—an indication of channel quality for a subband channel. The subband CQI may be fedback frequently.